In recent years, imaging optical systems have been strongly desired to be thinner. In order to deal with the shortening of the overall length by the optical design or the increase in error sensitivity caused thereby, the manufacturing accuracy has been improved; however, for dealing with the further desires, simply forming an image with one optical system and one imaging element as conventionally conducted has been insufficient. Therefore, an imaging optical system called a compound eye optical system has attracted attention for dealing with the desire for the thickness reduction. The compound eye optical system is an array optical system including a plurality of lenses disposed in the array shape, and forms an image with respect to an imaging region divided into a plurality of pieces in the imaging element. The obtained plural images are processed to be one image finally and output.
Various compound eye optical systems have been suggested in Patent Literatures 1 to 3 and Non-Patent Literature 1. For example, the compound eye optical system according to Patent Literature 1 includes a plurality of array optical systems that images the same field of view, and performs the super-resolution process using a small amount of difference in parallax thereof. The compound eye optical system according to Non-Patent Literature 1 is to divide the field of view with the decentering of one array optical system, and the compound eye optical system according to Patent Literatures 2 and 3 is to divide the field of view with the prism for changing the optical path.